Sheet stacking device, sheet post-processing device, and image forming system

ABSTRACT

A sheet stacking device includes a stacking tray, an aligning mechanism, a pair of alignment members, and a pair of height detectors. The pair of alignment members can move independently in a sheet width direction and in an up and down direction, and contact side edges in the sheet width direction of sheets stacked on the stacking tray, from both sides in the sheet width direction, so as to align the sheets in the sheet width direction. The pair of height detectors allow the pair of alignment members to contact an upper surface of the sheets near side edges of the sheets, so that sheet heights on both sides in the sheet width direction are detected. The sheet stacking device can individually correct heights of the pair of alignment members when aligning the sheets, based on the sheet heights detected by the pair of height detectors.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority fromthe corresponding Japanese Patent Application No. 2019-140728 filed Jul.31, 2019, the entire contents of which are hereby incorporated byreference.

BACKGROUND

The present disclosure relates to a sheet stacking device, a sheetpost-processing device including the sheet stacking device, and an imageforming system including the sheet post-processing device.

There is known a sheet post-processing device having a post-processingmechanism that performs post-processing such as a stapling process or apunching process after image formation. The sheet post-processing deviceis equipped with a sheet stacking device including a discharge rollerpair that discharges a sheet after the post-processing, and a stackingtray on which sheets discharged by a discharge roller pair are stacked.As the sheet stacking device, there is known a device including analigning mechanism for aligning sheets stacked on the stacking tray in asheet width direction perpendicular to a sheet discharge direction.

For instance, in the conventional sheet stacking device, when the amountof sheets stacked on the stacking tray increases, an alignment memberpair is moved down, and a position of the alignment member pair iscontrolled so that the alignment member pair contacts the sheets on thestacking tray. In this way, even if the sheets stacked on the stackingtray is curled (curved), the sheets can be securely aligned.

SUMMARY

A sheet stacking device according to one aspect of the presentdisclosure includes a sheet discharge outlet, a discharge roller pair, astacking tray, and an aligning mechanism. A sheet is discharged from thesheet discharge outlet. The discharge roller pair discharges the sheetfrom the sheet discharge outlet. The stacking tray is disposed below adownstream side of the sheet discharge outlet in a sheet dischargedirection, so that the sheet discharged from the sheet discharge outletby the discharge roller pair is stacked on the stacking tray. Thealigning mechanism aligns the sheets stacked on the stacking tray in asheet width direction perpendicular to the sheet discharge direction.The aligning mechanism includes a pair of alignment members and a pairof height detectors. The pair of alignment members are capable of movingindependently of each other in the sheet width direction and in an upand down direction, and contact side edges in the sheet width directionof the sheets stacked on the stacking tray from both sides in the sheetwidth direction, so as to align the sheets in the sheet width direction.The pair of height detectors detect heights of the sheets on both sidesin the sheet width direction by allowing the pair of alignment membersto contact an upper surface of the sheets at vicinities of the sideedges of the sheets. The pair of alignment members are is capable ofcorrecting heights of the pair of alignment members individually whenaligning the sheets, on the basis of the heights of the sheets detectedby the pair of height detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front cross-sectional diagram illustrating a schematicstructure of an image forming system of an embodiment of the presentdisclosure.

FIG. 2 is a partial front cross-sectional diagram illustrating a sheetstacking device and its vicinity in a sheet post-processing device ofthe embodiment of the present disclosure.

FIG. 3 is a perspective view of a sheet stacking device of theembodiment of the present disclosure.

FIG. 4 is a front cross-sectional diagram illustrating an alignmentmember and its vicinity in the sheet stacking device of the embodimentof the present disclosure.

FIG. 5 is a perspective view of the alignment member and its vicinity inthe sheet stacking device of the embodiment of the present disclosure.

FIG. 6 is a perspective view illustrating a cylindrical part and itsvicinity of the alignment member of the sheet stacking device of theembodiment of the present disclosure.

FIG. 7 is a perspective view illustrating the cylindrical part and itsvicinity of the alignment member of the sheet stacking device of theembodiment of the present disclosure.

FIG. 8 is a schematic front view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a statewhere the alignment member is at a first position.

FIG. 9 is a schematic front view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a statewhere the alignment member is at a second position.

FIG. 10 is a schematic front view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a statewhere one of the alignment members contacts an upper surface of sheets.

FIG. 11 is a schematic front view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a statewhere the other alignment member contacts the upper surface of thesheet.

FIG. 12 is a perspective view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a sheetheight detection state.

FIG. 13 is a schematic front view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a statewhere one of the alignment members is moved to an alignment position.

FIG. 14 is a schematic front view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a statewhere the other alignment member is moved to the alignment position.

FIG. 15 is a perspective view of the sheet stacking device of theembodiment of the present disclosure, as a diagram illustrating a statewhere heights of the alignment members are adjusted individually on thebasis of sheet heights.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure is described withreference to the drawings. Note that the present disclosure is notlimited to the following description.

FIG. 1 is a front cross-sectional diagram illustrating a schematicstructure of an image forming system 301 of the embodiment. The imageforming system 301 includes an image forming apparatus 101 and a sheetpost-processing device 201.

The image forming apparatus 101 is, for example, a so-called monochromemultifunction peripheral having functions such as printing, scanning(image reading), and facsimile transmitting. Note that the image formingapparatus 101 may be, for example, an apparatus such as a copier or aprinter, and it may be an apparatus that supports color printing.

As illustrated in FIG. 1, the image forming apparatus 101 includes adocument feeder unit 103 disposed on an upper surface of its main body102, and an image reader unit 104 disposed in the main body 102 belowthe document feeder unit 103. The image reader unit 104 reads an imageof a document loaded on the document feeder unit 103 or an image of adocument placed on a not shown contact glass on the upper surface of theimage reader unit 104.

The image forming apparatus 101 further includes a sheet feeding unit105, a sheet conveying unit 106, an exposure unit 107, an image formingunit 108, a transfer unit 109, a fixing unit 110, a sheet discharge unit111, and a main body controller 112.

The sheet feeding unit 105 stores a plurality of sheets S and sendingout the sheet S after separating one by one. The sheet conveying unit106 conveys the sheet S sent out from the sheet feeding unit 105 to thetransfer unit 109 and the fixing unit 110, and further delivers thesheet S after fixing, to the sheet discharge unit 111 or to the sheetpost-processing device 201. The exposure unit 107 emits a laser beamcontrolled based on image data to the image forming unit 108.

The image forming unit 108 includes a photosensitive drum 1081 as animage carrier and a development device 1082. In the image forming unit108, the laser beam emitted from the exposure unit 107 forms anelectrostatic latent image of a document image on a surface of thephotosensitive drum 1081. The development device 1082 supplies toner tothis electrostatic latent image to develop the image, so that a tonerimage is formed. The transfer unit 109 transfers the toner image formedby the image forming unit 108 on the surface of the photosensitive drum1081 to the sheet S. The fixing unit 110 heats and presses the sheet Swith the transferred toner image so that the toner image is fixed to thesheet S.

The sheet S after fixing is sent to the sheet discharge unit 111 or tothe sheet post-processing device 201. The sheet discharge unit 111 isdisposed below the image reader unit 104. The sheet discharge unit 111has an opening at the front, and the sheet after printing (printedmatter) is taken out from the front side. The sheet post-processingdevice 201 will be described later.

The main body controller 112 includes a CPU, an image processor, and astorage unit, which are not shown, and other not shown electroniccircuits and components. The CPU controls operations of the individualunits of the image forming apparatus 101 on the basis of controlprograms and data stored in the storage unit, so as to perform processesrelated to the functions of the image forming apparatus 101. The sheetfeeding unit 105, the sheet conveying unit 106, the exposure unit 107,the image forming unit 108, the transfer unit 109, and the fixing unit110 respectively receive instructions from the main body controller 112and perform printing on the sheet S in a cooperative manner. The storageunit is constituted of a combination of a nonvolatile storage devicesuch as a program read only memory (ROM) and a data ROM, and a volatilestorage device such as a random access memory (RAM), which are notshown, for example.

The sheet post-processing device 201 is connected to a side face of theimage forming apparatus 101 in a detachable and attachable manner. Notethat the sheet post-processing device 201 can be connected not only tothe multifunction peripheral but also to other apparatus such as acopier or a printer, for example. As illustrated in FIG. 1, the sheetpost-processing device 201 includes a sheet conveyance inlet 202, asheet discharge passage 203, an intermediate roller pair 204, aprocessing tray 205, a post-processor 206, a sheet stacking device 1,and a post-processing controller 207. Note that in the followingdescription about the sheet post-processing device 201, the directionfrom the right to the left in FIG. 1 is referred to as a “sheetdischarge direction”.

The sheet conveyance inlet 202 is formed and opens on a side surfacefacing the image forming apparatus 101. The sheet S after fixing, whichis delivered to the sheet post-processing device 201, passes through thesheet conveyance inlet 202 and is conveyed to an inside of the sheetpost-processing device 201.

The sheet discharge passage 203 extends laterally from the sheetconveyance inlet 202 to above the processing tray 205 in a directionapart from the image forming apparatus 101 (in the left direction inFIG. 1).

The intermediate roller pair 204 is disposed on the downstream side inthe sheet discharge direction of a punching unit 2061 (described later)in the sheet discharge passage 203. Rotation axes of the intermediateroller pair 204 extend in the sheet width direction perpendicular to thesheet discharge direction (in the direction perpendicular to paper ofFIG. 1). A plurality of the intermediate roller pairs 204 are arrangedwith spaces along the sheet width direction. The intermediate rollerpairs 204 convey the sheet S, which is conveyed in the sheet dischargepassage 203, to a sheet discharge outlet 2 (described later) on thefurther downstream side.

The processing tray 205 is disposed below the downstream side of thesheet discharge passage 203 in the sheet discharge direction. In otherwords, the processing tray 205 is positioned just below the downstreamside of the intermediate roller pairs 204 in the sheet dischargedirection. A sheet loading surface of the processing tray 205 has aninclination ascending toward the downstream side in the sheet dischargedirection. A plurality of sheets S conveyed to the processing tray 205through the sheet discharge passage 203 are loaded on the processingtray 205, and post-processing is performed on them.

The post-processor 206 performs a predetermined post-processing on thesheets S that are conveyed through the sheet discharge passage 203. Thepost-processor 206 includes the punching unit 2061 and a stapling unit2062, for example.

The punching unit 2061 is disposed at an intermediate part of the sheetdischarge passage 203 between the sheet conveyance inlet 202 as anupstream end and a downstream end in the sheet discharge direction. Thesheet post-processing device 201 performs a punching process on thesheet S conveyed in the sheet discharge passage 203, using the punchingunit 2061, so that punch holes can be formed.

The stapling unit 2062 is disposed on the upstream side of theprocessing tray 205 in the sheet discharge direction. The sheetpost-processing device 201 performs a stapling process (binding process)on the sheets S loaded on the processing tray 205, using the staplingunit 2062, so that the sheets can be bound.

The sheet stacking device 1 is disposed on the downstream side of theprocessing tray 205 in the sheet discharge direction. The sheet stackingdevice 1 includes a discharge roller pair 3, and a stacking tray 5. Thedischarge roller pair 3 is disposed at a downstream end of theprocessing tray 205 in the sheet discharge direction. The stacking tray5 is disposed below the downstream side of the discharge roller pair 3in the sheet discharge direction. The sheets S after finishing thepost-processing on the processing tray 205 are discharged by thedischarge roller pair 3 onto the stacking tray 5 and are taken out. Notethat if the post-processing by the stapling unit 2062 is not performed,the sheet S is not stacked on the processing tray 205 but is conveyed tothe stacking tray 5. A detailed structure of the sheet stacking device 1will be described later.

The post-processing controller 207 includes a CPU and a storage unit,which are not shown, and other not shown electronic circuits andcomponents. The post-processing controller 207 is connected to the mainbody controller 112 in a communicable manner. The post-processingcontroller 207 receives instructions from the main body controller 112,and uses the CPU to control operations of individual units of the sheetpost-processing device 201 on the basis of control programs and datastored in the storage unit, so as to perform processes related tofunctions of the sheet post-processing device 201. The sheet dischargepassage 203, the intermediate roller pair 204, the processing tray 205,the post-processor 206, and the sheet stacking device 1 respectivelyreceive instructions from the post-processing controller 207 and performpost-processing on the sheets S in a cooperative manner. Note that thepost-processing controller 207 is an example of the “controller” recitedin claim 1 of the present disclosure. The “controller” may be separatelydisposed in the sheet stacking device 1 itself.

Next, a detailed structure of the sheet stacking device 1 is describedwith reference to FIGS. 2, 3, 4, and 5. FIG. 2 is a partial frontcross-sectional diagram illustrating the sheet stacking device 1 and itsvicinity in the sheet post-processing device 201. FIG. 3 is aperspective view of the sheet stacking device 1. FIG. 4 is a frontcross-sectional diagram illustrating an alignment member 61 and itsvicinity in the sheet stacking device 1. FIG. 5 is a perspective viewillustrating the alignment member 61 and its vicinity in the sheetstacking device 1. FIGS. 6 and 7 are perspective views illustrating acylindrical part 611 and its vicinity in the alignment member 61 of thesheet stacking device 1.

Note that in the following description about the sheet stacking device1, the direction from the right to the left in FIGS. 2 and 4 is referredto as the “sheet discharge direction” and is shown by an arrow line Dd.Further, the “sheet width direction” perpendicular to the sheetdischarge direction is the direction perpendicular to papers of FIG. 2and FIG. 4, and is shown by an arrow line Dw in FIGS. 3 and 5.

As illustrated in FIG. 2, the sheet stacking device 1 includes the sheetdischarge outlet 2, the discharge roller pair 3, an arm part 4, thestacking tray 5, and an aligning mechanism 6.

The sheet discharge outlet 2 is disposed on the downstream side of theintermediate roller pair 204 in the sheet discharge direction Dd, and onthe downstream side of the processing tray 205 in the sheet dischargedirection Dd. The discharge roller pair 3 is disposed at the sheetdischarge outlet 2. The sheets S after finishing the post-processing onthe processing tray 205 are discharged onto the stacking tray 5 throughthe sheet discharge outlet 2.

The discharge roller pair 3 is disposed at the sheet discharge outlet 2.The discharge roller pair 3 discharges the sheet S from the sheetdischarge outlet 2. Rotation axes of the discharge roller pair 3 extendin the sheet width direction Dw. A plurality of the discharge rollerpairs 3 are arranged with spaces along the sheet width direction Dw. Inthis embodiment, as illustrated in FIG. 3, two discharge roller pairs 3are disposed. The discharge roller pair 3 includes a pair of a lowerside discharge roller 31 and an upper side discharge roller 32.

The lower side discharge roller 31 is connected to a not shown dischargedrive unit and can rotate in a forward direction for discharging thesheet S onto the stacking tray 5 and in a backward direction for sendingthe sheet S onto the processing tray 205. The upper side dischargeroller 32 contacts the lower side discharge roller 31 and is driven torotate.

The upper side discharge roller 32 is supported by the arm part 4. Thearm part 4 extends in the sheet discharge direction Dd, and supports theupper side discharge roller 32 in a rotatable manner, at one end on thedownstream end in the sheet discharge direction Dd.

The arm part 4 is supported by the sheet post-processing device 201 in arotatable manner about the rotation shaft 41 extending in the sheetwidth direction Dw, at one end on the upstream end in the sheetdischarge direction Dd. The arm part 4 is connected to a not shown armdrive unit, and is swung in the up and down direction about the rotationshaft 41 with a free end that is the one end supporting the upper sidedischarge roller 32. This swinging of the arm part 4 causes the upperside discharge roller 32 to contact or separate from the lower sidedischarge roller 31. As illustrated in FIGS. 2 and 3, the pair of upperside discharge roller 32 and the lower side discharge roller 31 contacteach other at their circumferential surfaces, and hence a nip 3N isformed for discharging the sheet S from the sheet discharge outlet 2.

The sheet S discharged from the sheet discharge outlet 2 by forwardrotation of the discharge roller pair 3 is stacked on the stacking tray5. Further, the nip 3N of the discharge roller pair 3 holds the sheet S,and in the state where the upstream end of the sheet S in the dischargedirection is apart from a nip 204N of the intermediate roller pair 204,the discharge roller pair 3 is rotated backward. Then, the sheet S isconveyed onto the processing tray 205.

The stacking tray 5 is disposed below the downstream side of the sheetdischarge outlet 2 in the sheet discharge direction Dd. A sheet stackingsurface 51 of the stacking tray 5 has an inclination ascending towardthe downstream side in the sheet discharge direction Dd. The upstreamend of the stacking tray 5 in the sheet discharge direction Dd ispositioned below the sheet discharge outlet 2. A sheet receiving wall 1a is disposed on the upstream side of the stacking tray 5 in the sheetdischarge direction Dd. The stacking tray 5 can be moved substantiallyvertically in the up and down direction by a not shown drive unit. Thesheet S discharged from the sheet discharge outlet 2 by the dischargeroller pair 3 is stacked on the stacking tray 5. The stacking tray 5 isa final discharge place of the sheet S, in the sheet post-processingdevice 201.

The stacking tray 5 has a recess 52. The recess 52 is recessed downwardfrom the sheet stacking surface 51 of the stacking tray 5. The recess 52is disposed on each side of the stacking tray 5 in the sheet widthdirection Dw with respect to a middle part in the sheet width directionDw. In general, when performing the aligning operation for aligning thesheets S in the sheet width direction Dw, the aligning operation isperformed in the state where a lower part of the alignment member 61described later is in the recess 52 as illustrated in FIG. 2.

As illustrated in FIGS. 2 and 3, the aligning mechanism 6 is disposedabove the sheet discharge outlet 2 on the downstream side thereof in thesheet discharge direction Dd, and on each side in the sheet widthdirection Dw. The aligning mechanism 6 aligns the sheets S stacked onthe stacking tray 5 in the sheet width direction Dw perpendicular to thesheet discharge direction Dd. The operation of the aligning mechanism 6is controlled by the post-processing controller 207, for example.

The aligning mechanisms 6 are disposed to form a pair on both sides ofthe sheets S stacked on the stacking tray 5 in the sheet width directionDw. The pair of aligning mechanisms 6 includes an aligning mechanism 6Fdisposed on the front side of the sheet stacking device 1 and analigning mechanism 6B disposed on the back side of the same with respectto the sheets S. Unless it is necessary to specify, the suffixes F and Brepresenting front and back, respectively, may be omitted.

Each of the pair of aligning mechanisms 6 includes the alignment member61, a slide mechanism 7, a lifting mechanism 8, and a height detector62. In other words, the aligning mechanisms 6 include a pair ofalignment members 61 and a pair of height detectors 62. The pair ofaligning mechanisms 6 have the basically same structure except that thealignment members 61 align the sheets S in the opposite directions inthe sheet width direction Dw.

The alignment member 61 is disposed on the downstream side of the sheetdischarge outlet 2 in the sheet discharge direction Dd and on one endside of the stacking tray 5 in the sheet width direction Dw. Thealignment member 61 is held by a carriage 72 described later of theslide mechanism 7. The alignment member 61 has a plate-like shape thatextends in the sheet discharge direction Dd and has a substantially Lshape viewed from the sheet width direction Dw. The alignment member 61includes the cylindrical part 611 and a sheet contact part 612.

The cylindrical part 611 is disposed at an upstream end in the sheetdischarge direction Dd and the upper end of the alignment member 61, andextends in the sheet width direction Dw. The cylindrical part 611 has athrough hole 6111 extending in the sheet width direction Dw, in which arotation shaft 721 of the carriage 72 is inserted. The cylindrical part611 is supported by the rotation shaft 721 of the carriage 72 in arotatable manner. In other words, the alignment member 61 can rotateabout the rotation shaft 721 with respect to the carriage 72. A moredetailed structure of the cylindrical part 611 will be describedtogether with description of the lifting mechanism 8 described later.

The sheet contact part 612 is disposed at a downstream side part of thealignment member 61 in the sheet discharge direction Dd and in an areafacing the sheets S stacked on the stacking tray 5. The sheet contactpart 612 contacts the side edges of the sheets S stacked on the stackingtray 5 in the sheet width direction Dw from one end side in the sheetwidth direction Dw.

The pair of alignment members 61 can be moved independently of eachother, in the sheet width direction Dw and in the up and down direction,by the slide mechanism 7 and the lifting mechanism 8.

The slide mechanism 7 is disposed above the sheet discharge outlet 2.The slide mechanism 7 includes a guide shaft 71, the carriage 72, and anot shown width direction drive unit.

The guide shaft 71 is disposed at an upper part of the slide mechanism7, extends in the sheet width direction Dw, and is supported by thesheet post-processing device 201.

The guide shaft 71 penetrates the carriage 72 in the sheet widthdirection Dw, and the carriage 72 is supported by the guide shaft 71.The carriage 72 can move in the sheet width direction Dw along the guideshaft 71. The carriage 72 includes the rotation shaft 721 and holds thealignment member 61 via the rotation shaft 721.

The width direction drive unit may be constituted of, for example, anendless moving belt extending in the sheet width direction Dw, to whichthe carriage 72 is attached, a pulley around which the moving belt iswound, a drive motor for rotating the pulley, and the like.Alternatively, the width direction drive unit may be constituted of, forexample, a rack extending in the sheet width direction Dw, a pinionattached to the carriage 72 so as to engage with the rack, a drive motorfor rotating the pinion, and the like.

The slide mechanism 7 can move the carriage 72 holding the alignmentmember 61 in the sheet width direction Dw along the guide shaft 71 byoperating the drive motor of the width direction drive unit. In otherwords, the slide mechanism 7 moves each of the pair of alignment members61 in the sheet width direction Dw. In this way, the pair of alignmentmembers 61 contact the side edges in the sheet width direction Dw of thesheets S stacked on the stacking tray 5 from both sides in the sheetwidth direction Dw, so as to align the sheets S in the sheet widthdirection Dw.

The lifting mechanism 8 is disposed inside the carriage 72 and outsidethe sheet discharge outlet 2 in the sheet width direction Dw. Thelifting mechanism 8 includes an output gear 81, an intermediate gear 82,a drive transmission gear 83, a drive shaft 84, an input gear 85, and adrive motor 86.

An output gear 81 is disposed at a bottom inside the carriage 72. Theoutput gear 81 has a through hole 811 extending in the sheet widthdirection Dw, in which the rotation shaft 721 of the carriage 72 isinserted, and is supported by the carriage 72. The output gear 81 isdisposed coaxially with the cylindrical part 611 of the alignment member61, and can rotate about the rotation shaft 721 extending in the sheetwidth direction Dw.

The output gear 81 has a protrusion 812. The protrusion 812 is disposedon a side face of the output gear 81, which faces the cylindrical part611 of the alignment member 61, and protrudes toward the cylindricalpart 611 in the sheet width direction Dw. The protrusion 812 is formedin a sector shape having a center at the axis viewed from the sheetwidth direction Dw, for example. For instance, two protrusions 812 aredisposed at symmetric positions with respect to the axis center.

The cylindrical part 611 has recesses 6112. The recesses 6112 aredisposed at a side face of the cylindrical part 611 facing the outputgear 81, and recess toward inside of the cylindrical part 611 in thesheet width direction Dw. The recess 6112 is formed in a sector shapehaving a center at the axis viewed from the sheet width direction Dw,for example. A perimeter of the recess 6112 in a radial direction opensin a circumferential surface of the cylindrical part 611. For instance,two recesses 6112 are disposed at symmetric positions with respect tothe axis center.

The protrusion 812 of the output gear 81 is inserted in the recess 6112of the cylindrical part 611 along the sheet width direction Dw (see FIG.8). A central angle of the recess 6112 having a sector shape viewed fromthe sheet width direction Dw is larger than that of the protrusion 812having a sector shape similarly. For instance, the recess 6112 is formedto have a central angle of 90 degrees, and the protrusion 812 can moveabout the rotation shaft 721 within a movable area Ar of approximately60 degrees in the recess 6112. In other words, the pair of alignmentmembers 61 are attached to one end and the other end of the rotationshaft 721 respectively in a rotatable manner with a predetermined playin the rotation direction.

The intermediate gear 82 is disposed above the output gear 81 inside thecarriage 72, and is supported by the carriage 72. The intermediate gear82 is engaged with the output gear 81 and can rotate about an axisextending in the sheet width direction Dw.

The drive transmission gear 83 is disposed above the intermediate gear82 inside the carriage 72 and is supported by the carriage 72. The drivetransmission gear 83 is engaged with the intermediate gear 82. The drivetransmission gear 83 is disposed coaxially with the drive shaft 84 andcan rotate around an axis extending in the sheet width direction Dw.

The drive shaft 84 is disposed in the middle of the carriage 72 in theup and down direction, extends in the sheet width direction Dw, and issupported by the sheet post-processing device 201 in a rotatable manner.The drive shaft 84 penetrates the carriage 72 in the sheet widthdirection Dw, and the drive transmission gear 83 is disposed coaxiallywith the drive shaft 84. The carriage 72 can move in the sheet widthdirection Dw along the guide shaft 71 with respect to the drive shaft 84and does not rotate together with the drive shaft 84. The drivetransmission gear 83 can move together with the carriage 72 in the sheetwidth direction Dw with respect to the drive shaft 84, and rotatesfollowing the rotation of the drive shaft 84.

The input gear 85 is disposed on one end side of the sheet dischargeoutlet 2 in the sheet width direction Dw, and is fixed to one end of thedrive shaft 84 in the sheet width direction Dw. The input gear 85 isdisposed coaxially with the drive shaft 84 and can rotate about an axisextending in the sheet width direction Dw.

The drive motor 86 is disposed on one end side of the sheet dischargeoutlet 2 in the sheet width direction Dw. The drive motor 86 isconstituted of a stepping motor or the like, for example. A rotationshaft of the drive motor 86 is provided with a not shown drive gear. Thedrive gear of the rotation shaft of the drive motor 86 is engaged withthe input gear 85.

Note that a not shown one-way rotary member is disposed between therotation shaft of the drive motor 86 and the input gear 85. Duringrotation of the drive motor 86, if the input gear 85 and the drive shaft84 stop rotating so that a load is generated due to contact between thealignment member 61 and the sheet S, the drive motor 86 idles due to theone-way rotary member's action. In this way, the drive motor 86 can beprevented from being broken.

The lifting mechanism 8 operates the drive motor 86, and hence canrotate the alignment member 61 about the rotation shaft 721 extending inthe sheet width direction Dw, via the input gear 85, the drive shaft 84,the drive transmission gear 83, the intermediate gear 82, and the outputgear 81. In this way, the sheet contact part 612 of the alignment member61 moves in the up and down direction. In other words, the liftingmechanism 8 can move the alignment member 61 in the up and downdirection.

The height detector 62 is disposed on the one end side of the sheetdischarge outlet 2 in the sheet width direction Dw, for example. Theheight detector 62 includes a magnetic or optical angle detection sensor621 including a rotary encoder or a resolver, and can detect a rotationangle of the alignment member 61 that rotates about the rotation shaft721. In other words, the height detector 62 can detect a position of thealignment member 61 in the up and down direction.

As described above, the lifting mechanism 8 can move the alignmentmember 61 in the up and down direction. Then, the height detectors 62detect heights of the sheets S at both sides in the sheet widthdirection Dw, by allowing the pair of alignment members 61 to contactthe upper surface of the sheets S stacked on the stacking tray 5 nearthe side edges of the sheets S.

Next, an operation of the sheet stacking device 1 is described withreference to FIG. 3 as well as FIGS. 8 to 15. Note that for conveniencesake of description, FIGS. 8, 9, 10, 11, 13, and 14 show a front view ofonly one of the pair of alignment members 61 and, on the right sidethereof, enlarged cross-sectional views of the protrusion 812 of theoutput gear 81 and the cylindrical part 611, for describing a positionalrelationship of the alignment member 61. Further, suffixes F and Brepresenting front and back, respectively, of the sheet stacking device1 with respect to the sheets S are added for the alignment member 61, asnecessary.

Usually every time when one sheet S is discharged onto the stacking tray5, the sheet stacking device 1 performs the aligning operation of thesheets S stacked on the stacking tray 5. In this case, as illustrated inFIG. 3, the aligning mechanism 6 allows the pair of alignment members 61to contact the side edges in the sheet width direction Dw of the sheetsS stacked on the stacking tray 5 from both sides in the sheet widthdirection Dw. Note that a distance between the pair of alignment members61 in the sheet width direction Dw is determined in advance on the basisof a size of the sheets S stacked on the stacking tray 5.

As illustrated in FIG. 3, a part of the sheets S stacked on the stackingtray 5 may be curved, and hence a curled part Sc may be generated. Forthis reason, when a print job is finished, or every time when apredetermined number of sheets S are discharged onto the stacking tray5, the sheet stacking device 1 performs height detection of the sheets Sstacked on the stacking tray 5 using the pair of height detectors 62,and can perform the aligning operation by correcting the heights of thepair of alignment members 61 individually from each other.

FIG. 8 is a schematic front view of the sheet stacking device 1, as adiagram illustrating a state where the alignment member 61 is at a firstposition P1. As illustrated in FIG. 8, the post-processing controller207 first controls each of the pair of alignment members 61 to move tothe first position P1 facing the side edges in the sheet width directionDw of the sheets S stacked on the stacking tray 5. The first position P1of the pair of alignment members 61 is a position of the pair ofalignment members 61 in the normal aligning operation, in which thealignment member 61 is close to the stacking tray 5 in the up and downdirection, and the lower part thereof is in the recess 52. The firstposition P1 of the pair of alignment members 61 is a position outsidethe side edges of the sheets S in the sheet width direction Dw, in whichthe alignment member 61 does not contact the sheets S.

The post-processing controller 207 stops rotation of the protrusion 812of the output gear 81 of the lifting mechanism 8 at a predeterminedposition corresponding to the first position P1. Each of the pair ofalignment members 61 tries to rotate in a counterclockwise direction inFIG. 8 due to gravity action, but one end part in the circumferentialdirection of the recess 6112 of the cylindrical part 611 abuts theprotrusion 812 so that the rotation stops at the first position P1.

FIG. 9 is a schematic front view of the sheet stacking device 1, as adiagram illustrating a state where the alignment member 61 is at asecond position P2. Next, as illustrated in FIG. 9, the post-processingcontroller 207 controls the lifting mechanism 8 to move each of the pairof alignment members 61 from the first position P1 to the secondposition P2 above the sheets S. The second position P2 of the pair ofalignment members 61 is set to a sufficiently high position taking intoaccount the number of sheets S and the curl.

The post-processing controller 207 allows the protrusion 812 of theoutput gear 81 of the lifting mechanism 8 to rotate in a clockwisedirection in FIG. 9 from the first position P1 by 50 degrees, forexample, to be at the second position P2. When the cylindrical part 611is rotated by the protrusion 812, each of the pair of alignment members61 is rotated about the rotation shaft 721 and is moved to the secondposition P2.

The movable area Ar of the protrusion 812 in the recess 6112 illustratedin FIG. 8 is 60 degrees, and the rotation angle from the first positionP1 to the second position P2 is 50 degrees. Therefore, after being atthe second position P2, even when the alignment member 61 soon contactsthe sheet S and stops its rotation, the protrusion 812, which continuesto rotate after that until reaching the position corresponding to thefirst position P1, does not contact the opposite end of the recess 6112in the circumferential direction. In this way, an overload does notoccur, and a breakage of the output gear 81 or the cylindrical part 611can be prevented.

Next, the post-processing controller 207 controls the slide mechanism 7to move each of the pair of alignment members 61 to inside in the sheetwidth direction Dw so as to be positioned at a third position P3 (seeFIG. 10) facing the upper surface of the sheets S. Here, thepost-processing controller 207 controls the angle detection sensor 621of the height detector 62 to detect a position (angle) of the alignmentmember 61 at the third position P3 in the up and down direction, andstores the same as an initial value.

FIG. 10 is a schematic front view of the sheet stacking device 1, as adiagram illustrating a state where one alignment member 61F contacts theupper surface of the sheets S. Next, as illustrated in FIG. 10, thepost-processing controller 207 controls the lifting mechanism 8 to moveeach of the pair of alignment members 61 downward from the thirdposition P3 so as to contact the upper surface of the sheets S. Asillustrated in FIG. 3, if the sheets S stacked on the stacking tray 5have a curved part, i.e. a curled part Sc on the front side, the frontside alignment member 61F contacts the upper surface of the sheets Searlier than a back side alignment member 61B does (see FIG. 10).

The post-processing controller 207 allows the protrusion 812 of theoutput gear 81 of the lifting mechanism 8 to rotate from the thirdposition P3 in the counterclockwise direction in FIG. 10. Due to gravityapplied to each of the pair of alignment members 61, the cylindricalpart 611 rotates together with the protrusion 812, and hence each of thepair of alignment members 61 is rotated about the rotation shaft 721toward the upper surface of the sheets S. When the front side alignmentmember 61F contacts the upper surface of the sheets S, it stops at thecontact position Pt.

Note that when the front side alignment member 61F contacts the uppersurface of the sheets S and stops at the contact position Pt, theprotrusion 812 of the output gear 81 of the lifting mechanism 8continues to rotate in the counterclockwise direction in FIG. 10. Inthis way, the back side alignment member 61B is rotated about therotation shaft 721 toward the upper surface of the sheets S.

FIG. 11 is a schematic front view of the sheet stacking device 1, as adiagram illustrating a state where the other alignment member 61Bcontacts the upper surface of the sheets S. FIG. 12 is a perspectiveview of the sheet stacking device 1, as a diagram illustrating a sheetheight detection state. As illustrated in FIG. 3, if the sheets Sstacked on the stacking tray 5 have no curled part and are flat on theback side, the back side alignment member 61B contacts the upper surfaceof the sheets S at a normal height (see FIGS. 11 and 12). When the backside alignment member 61B contacts the upper surface of the sheets S, itstops at the contact position Pt.

Note that when the back side alignment member 61B contacts the uppersurface of the sheets S and stops at the contact position Pt, theprotrusion 812 of the output gear 81 of the lifting mechanism 8continues to rotate in the counterclockwise direction in FIG. 11. Afterthat, the protrusion 812 rotates to a position corresponding to thefirst position P1, and stops.

Next, the post-processing controller 207 controls the angle detectionsensor 621 of the height detector 62 to detect a position (angle) in theup and down direction of each of the pair of alignment members 61 thathas stopped. In addition, the post-processing controller 207 controlsthe angle detection sensor 621 to detect a rotation angle of each of thepair of alignment members 61 from the third position P3 stored as theinitial value to the contact position Pt. Then, the post-processingcontroller 207 derives an alignment position Pa of each of the pair ofalignment members 61 (see FIGS. 13 and 14) after correcting the heighton the basis of the rotation angle.

If the sheets S have no curled part and are flat, the first position P1may be set as the alignment position Pa of the back side alignmentmember 61B without the correction.

FIG. 13 is a schematic front view of the sheet stacking device 1, as adiagram illustrating a state where one of the alignment members 61B ismoved to the alignment position Pa. Next, as illustrated in FIG. 13, thepost-processing controller 207 positions the back side alignment member61B at the alignment position Pa. If the back side of the sheets Sstacked on the stacking tray 5 is flat, for example, the post-processingcontroller 207 sets the alignment position Pa of the back side alignmentmember 61B to the first position P1, and positions the alignment member61B.

The post-processing controller 207 stops the rotation of the protrusion812 of the output gear 81 of the back side lifting mechanism 8 at apredetermined position corresponding to the first position P1 that isthe alignment position Pa. The back side alignment member 61B stops atthe first position P1 as the alignment position Pa, when one end of therecess 6112 of the cylindrical part 611 in the circumferential directionabuts the protrusion 812 due to gravity action.

FIG. 14 is a schematic front view of the sheet stacking device 1, as adiagram illustrating a state where the other alignment member 61F ismoved to the alignment position Pa. Next, as illustrated in FIG. 14, thepost-processing controller 207 positions the front side alignment member61F at the alignment position Pa. The alignment position Pa of the backside alignment member 61B is corrected in the height on the basis of therotation angle of the front side alignment member 61F from the thirdposition P3 to the contact position Pt with the sheet S. Thepost-processing controller 207 positions the front side alignment member61F at the alignment position Pa after correcting the height.

The post-processing controller 207 stops the rotation of the protrusion812 of the output gear 81 of the front side lifting mechanism 8 at apredetermined position corresponding to the alignment position Pa aftercorrecting the height. The front side alignment member 61F stops at thealignment position Pa after correcting the height, when one end of therecess 6112 of the cylindrical part 611 in the circumferential directionabuts the protrusion 812 due to gravity action.

FIG. 15 is a perspective view of the sheet stacking device 1, as adiagram illustrating a state where the heights of the alignment members61 are individually corrected on the basis of the sheet heights. Next,as illustrated in FIG. 15, the post-processing controller 207 performsthe aligning operation for aligning the sheet S in the sheet widthdirection Dw at the alignment position Pa.

The post-processing controller 207 controls the slide mechanism 7 tomove the back side alignment member 61B in the sheet width direction Dwat the first position P1 as the alignment position Pa, so as to contactthe side edges in the sheet width direction Dw of the sheets S stackedon the stacking tray 5. Further, the post-processing controller 207controls the slide mechanism 7 to move the front side alignment member61F in the sheet width direction Dw at the alignment position Pa aftercorrecting the height, so as to contact the side edges in the sheetwidth direction Dw of the sheets S stacked on the stacking tray 5. Thealignment member 61F on the front side, where the sheets S has thecurled part Sc, contacts the side edges of the sheets S in the sheetwidth direction Dw at a position higher than the alignment member 61B onthe back side, where the sheets S are flat.

As described above, the aligning mechanism 6 can individually correctthe heights of the pair of alignment members 61 so that the pair ofalignment members 61 face the side edges of the sheet S when aligningthe sheets S, on the basis of the heights of the sheets S detected bythe pair of height detectors 62. With this structure, even if the sheetsS stacked on the stacking tray 5 are curled (curved) so that the heightthereof is different between both sides in the sheet width direction Dw,the heights of the pair of alignment members 61 can be correctedindividually. The heights of the pair of alignment members 61 can beindividually adjusted to the heights of the sheets S in accordance withthe heights of the sheets S detected by the pair of height detectors 62.In this way, the alignment members 61 can contact the side edges of thesheets S in the sheet width direction Dw in accordance with the heightsof the curled sheet S, and the sheets S on the stacking tray 5 can beappropriately aligned. In other words, a decrease in alignment propertyof the sheets S stacked on the stacking tray 5 or dropping of the samefrom the stacking tray 5 can be prevented.

Further, with the structure described above, the pair of alignmentmembers 61 can rotate about the rotation shaft 721 extending in thesheet width direction Dw, independently of each other. Further, theheight detector 62 detects the height of the sheets S on the basis ofthe rotation angle of the alignment member 61. In this way, the heightsof the sheets S can be easily detected by rotating the alignment members61. In addition, the heights of the sheets S can be detected with fineresolutions. Therefore, the heights of the pair of alignment members 61can be appropriately adjusted to the heights of the sheets S.

Note that if a difference between the height of the sheets S detected byone of the pair of height detectors 62 and the height of the sheetdetected by the other of the pair of height detectors is a predeterminedvalue or larger, the discharging of the sheets S from the sheetdischarge outlet 2 is stopped. With this structure, if the sheets S arecurled (curved) to such an extent that the movement of the alignmentmember 61 in the up and down direction does not work, it is possible tostop stacking the sheets S on the stacking tray 5. It is possible toprevent stacking on the stacking tray 5 of the sheets S that are largelycurled so that a decrease in alignment property or dropping from thestacking tray 5 may occur.

Further, according to the embodiment described above, each of the pairof alignment members 61 is attached to the rotation shaft 721 in arotatable manner with a predetermined play in the rotation direction.Further, the post-processing controller 207 allows each of the pair ofalignment members 61 to move from the first position P1 to the secondposition P2, and further to the third position P3, controls the angledetection sensor 621 to detect the rotation angle from the thirdposition P3 to the contact position Pt at which the alignment member 61contacts the upper surface of the sheets S and stops, derives thealignment position Pa after correcting the height based on the rotationangle, and performs the aligning operation for aligning the sheets S inthe sheet width direction at the alignment position Pa. With thisstructure, only by rotating the alignment member 61 about the rotationshaft 721 so as to move downward, the contact position Pt of thealignment member 61 with the sheets S can be detected. In this way, itis not necessary to use a sensor for detecting contact of the alignmentmember 61 with the sheets S. Therefore, cost reduction of the apparatuscan be achieved, and the alignment position Pa of the alignment member61 can be easily derived.

Further, according to the embodiment described above, the sheetpost-processing device 201 includes the sheet stacking device 1 havingthe structure described above. In this way, in the sheet post-processingdevice 201, if the height of the sheets S stacked on the stacking tray 5is different between both sides in the sheet width direction Dw, theheights of the pair of alignment members 61 can be adjusted individuallyto the heights of the sheets S. Therefore, in the sheet post-processingdevice 201, the alignment members 61 can contact the side edges of thesheets S in the sheet width direction Dw in accordance with the heightsof the sheets S, and the sheets S on the stacking tray 5 can beappropriately aligned.

Further, according to the embodiment described above, the image formingsystem 301 includes the sheet stacking device 1 having the structuredescribed above. In this way, in the image forming system 301, if theheight of the sheets S stacked on the stacking tray 5 is differentbetween both sides in the sheet width direction Dw, the heights of thepair of alignment members 61 can be adjusted individually to the heightsof the sheets S. Therefore, in the image forming system 301, thealignment members 61 can contact the side edges of the sheets S in thesheet width direction Dw in accordance with the heights of the sheets S,and the sheets S on the stacking tray 5 can be appropriately aligned.

Although the embodiment of the present disclosure is described above,the scope of the present disclosure is not limited to the embodiment,but can be variously modified within the scope of the invention withoutdeviating from the spirit thereof.

For instance, in the embodiment described above, the lifting mechanism 8rotates the alignment member 61 about the rotation shaft 721 so as tomove in the up and down direction, but this mechanism is not alimitation. For instance, the lifting mechanism 8 may be one that movesthe alignment member 61 to slide substantially vertically in the up anddown direction, or to slide in the up and down direction along thenormal direction to the sheet stacking surface 51 of the stacking tray5.

Further, in the embodiment described above, the image forming apparatus101 of the image forming system 301 is the image forming apparatus formonochrome printing, but this type is not a limitation. For instance,the image forming apparatus may be an image forming apparatus for colorprinting.

What is claimed is:
 1. A sheet stacking device comprising: a sheetdischarge outlet from which a sheet is discharged; a pair of dischargerollers for discharging the sheet from the sheet discharge outlet; astacking tray disposed below a downstream side of the sheet dischargeoutlet in a sheet discharge direction to stack the sheet discharged fromthe sheet discharge outlet; and an aligning mechanism for aligning thesheet stacked on the stacking tray in a sheet width directionperpendicular to the sheet discharge direction, wherein the aligningmechanism includes a pair of alignment members capable of movingindependently of each other in the sheet width direction and in an upand down direction, the pair of alignment members contacting side edgesin the sheet width direction of the sheet stacked on the stacking trayfrom both sides in the sheet width direction, so as to align the sheetin the sheet width direction, and a pair of height detectors fordetecting heights of the sheet on both sides in the sheet widthdirection by allowing the pair of alignment members to contact an uppersurface of the sheet at vicinities of the side edges of the sheet, andthe pair of alignment members can individually adjust the heights of thepair of alignment members so that the pair of alignment members face theside edges of the sheet when aligning the sheet, on the basis of theheights of the sheet detected by the pair of height detectors.
 2. Thesheet stacking device according to claim 1, wherein the pair ofalignment members are capable of rotating independently of each otherabout a rotation shaft extending in the sheet width direction, and thepair of height detectors detect the heights of the sheet on the basis ofrotation angles of the pair of alignment members.
 3. The sheet stackingdevice according to claim 1, wherein if a difference between the heightof the sheet detected by one of the pair of height detectors and theheight of the sheet detected by the other of the pair of heightdetectors is a predetermined value or larger, the discharging of thesheet from the sheet discharge outlet is stopped.
 4. The sheet stackingdevice according to claim 1, further comprising a controller forcontrolling an operation of the aligning mechanism, wherein the aligningmechanism includes a slide mechanism for moving each of the pair ofalignment members in the sheet width direction, and a lifting mechanismfor rotating each of the pair of alignment members about a rotationshaft in the up and down direction, the pair of alignment members areattached to one end and the other end of the rotation shaft respectivelyin a rotatable manner with a predetermined play in the rotationdirection, each of the pair of height detectors includes an angledetection sensor capable of detecting a rotation angle of the alignmentmember, and the controller controls the lifting mechanism to move eachof the pair of alignment members independently from a first positionfacing side edge in the sheet width direction of the sheet stacked onthe stacking tray to a second position above the sheet, then controlsthe slide mechanism to move each of the pair of alignment members toinside in the sheet width direction so as to be positioned at a thirdposition facing the upper surface of the sheet, then controls thelifting mechanism to move each of the pair of alignment members downwardfrom the third position to a contact position in contact with the uppersurface of the sheet, while controlling the angle detection sensor todetect a rotation angle from the third position to the contact position,then derives an alignment position of each of the pair of alignmentmembers after correcting height based on the rotation angle, and thenperforms an aligning operation for aligning the sheet in the sheet widthdirection at the alignment position.
 5. A sheet post-processing devicecomprising: a processing tray on which a sheet is loaded; apost-processor for performing a predetermined post-processing on thesheet loaded on the processing tray; and the sheet stacking deviceaccording to claim 1, including the pair of discharge rollers disposedon the downstream side of the processing tray in the sheet dischargedirection, so that the sheet after the post-processing by thepost-processor is stacked on the stacking tray by the pair of dischargerollers.
 6. An image forming system comprising: an image formingapparatus for forming an image on a sheet; and the sheet post-processingdevice according to claim 5, configured to be connected to the imageforming apparatus so as to perform a predetermined post-processing onthe sheet after image formation.